What is your correct takeoff point?

[PVstudent]

Please review the following videos:
Sergei Bubka
http://youtu.be/y9Q4rL0PC-s
Svetlana Feofanova
http://youtu.be/-TWAbc5TdpM
Annika Becker
http://youtu.be/xpfUUcjMRI4
Dmitri Markov
http://youtu.be/v9Ne--kuMUU

Consider the take-off showing identical body posture orientations at toe tip take-off of a tall and short stature vaulter. Both vaulters take exactly the same grip length measured from the pole tip to the top of the top hand grip. Each vaulter also makes identical grip-width spacing between the upper and lower hand locations on the pole.

Tall versus Shorter Vaulter at Take-OFF

Feofanova Plant Torques 6.jpg (63.52 KiB) Viewed 41374 times

With both hands gripped on the pole, the pole tip firmly located in contact with the deepest part of the planting box and the rear wall, the vaulter rises on to toe–tip with their body erect and both arms simultaneously positioned in the finish of the plant position.
Consensus coaching practice is for the vaulter’s upper grip arm to be fully extended in alignment with the ear whilst the head held in the neutral / anatomical position as the toe-tip, with torso held firmly erect, position is reached.
In real life some slight forward lean by the vaulter is required to maintain pressure through the pole-tip against the bottom of the rear wall to sustain a stable balance when fully raised on toe tip.
It is immediately obvious that the taller vaulter has:

(1) Higher reach upwards with the upper grip hand
(2) Greater pole ground angle (Angle B > A)
(3) Take-off toe tip location is closer horizontally along the runway surface in relationship to the pole tip located in the deepest part of the planting box.

The vaulter adjusts the location of their take-off foot toe position until a perpendicular line projected from the toe position on the runway intersects with the top of the upper hand grip on the pole.
The effective pole length is a constant (same length) for both a short and tall vaulter gripping the pole with identically located positions of the upper hand and between grip spacing.
By definition a right triangle will be formed with hypotenuse “C” (the constant effective pole length) for vaulters gripping the pole at the same grip length when the final toe-tip position indicated in the diagram and the pictures below is achieved.

Bubka Pythagoras and Laws of Similar Triangles Trigonometry.jpg (64.09 KiB) Viewed 41374 times

It follows from the Laws of Properties of Similar Triangles and Pythagorian Theory the toe –tip of the taller of two vaulters, who in all other respects is similar to the shorter, must be located closer in the horizontal direction (right triangle side A) to the pole tip contacting the rear wall when it is located in the deepest part of the planting box.
The vertex of the right triangle is side B. The height of side B is measured vertically from the deepest point in the planting box to the highest point of the position of the top grip hand at toe-tip take-off.

If the proposition that the pole ground angle (beta), (the angle between side A and the hypotenuse side C of the triangle) should be maximized to thereby minimize the angular distance the chord of the pole must travel (angle alpha) to pass through the transverse vertical plane from the pole tip in the planting box, is accepted the taller vaulter will have a distinct advantage in making the take-off.
Tall vaulters, because of their height, have higher pole ground angles at touch-down and at take-off and consequently have LESS pole chord angle to travel through to move past the transverse vertical plane from the pole tip located in the planting box. Also a tall vaulter has less horizontal displacement to travel before passing through the transverse vertical plane of the pole chord when the pole is fully straight at the end of its recoil phase (all other factors being the same for both vaulters).

For any individual vaulter, if the proposition holds true in real life, a decrease in effective grip length on the pole should result in the vaulter’s take-off foot toe tip location on the runway being horizontally closer to the rear wall of the planting box. Consequently the pole ground angle should also be greater at the take-off from this closer location (assuming the postural configuration and vertex height from toe tip to highest point on the top hand grip(side B) remains constant for that particular vaulter.
The vertex height can also be considered to be a constant of fixed length because of the:

(1) Unique anthropometric proportions of the individual vaulter
(2) Chosen grip length apart of the upper and lower hand being kept the same for all vaults
(3) Lower grip arm position and orientation with respect to the shoulder joint is also kept the same for all vaults.

***The maximum vertical reach height obtainable by the upper hand, no matter what the length along the pole at which it is located, is primarily determined by the precise 3 Dimensional location of the lower hand grip at the instant the pole tip makes initial contact with the rear wall of the planting box.

This is a fact beyond dispute and confirmable by simple empirical experiment suggested below.

With the pole tip located in the deepest part of the planting box, find the toe-tip location that maximizes the pole ground angle with both hands gripping the pole. Release the top hand grip and extend the lower grip hand vertically upwards maintaining its same grip location on the pole.
When the maximum height holding the pole with the lower grip arm extended upward is achieved, the vaulter with upper grip arm fully extended and aligned to the ear (note does not need to be touching the ear!) will fail to grasp the pole at the same exact grip width along the inclined pole that was possible when it was gripped by both hands.
Note that when the lower grip only is used the vaulter will have to move the take-off foot toe tip horizontally forward because the pole ground angle (beta) will noticeably increase until a right triangle is formed by the pole and the body alignment of the vaulter. The gain in vertex height required of the top hand grip location obtained when holding the pole by the lower arm only, proportionally decreases the horizontal distance back along the runway to the take-off toe tip.

When coaches suggest that the vaulter is “under” or “out” they are, tacitly or explicitly, expressing awareness of the proportional relationships they have observed in the attempt by the vaulter.

Having observed the movement possibly using their “intuition” or the “yardsticks” provided by millennia old geometric and mathematical principles, experienced coaches and vaulters are able to make finely discriminated spatial judgements. This is especially the case with respect to take-off foot placement and the visualized vertical line between the top grip hand placement on the pole and a point where it intersects the surface of the runway.

On this basis the geometric and triangle relationship hypothesis offered, predicts that there is a precise location for the toe tip of the take-off foot in pole vaulting.

This hypothesis (theoretical (conceptual) model) has as its central tenet the proposition that the major objective of the vaulter in effecting a pole vault take-off is, to maximize the pole ground angle at the instant the take-off foot toe tip no longer contacts the ground.
The theoretical model predicts that the precise point of the take-off toe tip location will occur at variable horizontal distances with respect to the rear wall according to the particular grip length along the pole and its associated grip spacing between the hands chosen by a specific vaulter for a particular vault attempt.

My position is that my empirical observations and experiences of real pole vaulting do not falsify this hypothesis!

Therefore I strongly maintain my belief that there is an “ideal correct take-off location” that is precise and specific to each vaulter and is primarily determined by the grip length and hand grip separation width on the pole chosen by them for a particular vault attempt.

The strength of my belief relies on geometrical and mathematical laws that give repeatable, precise and accurate predictions, so far as I am aware, that are corroborated empirically by practicing pole vault coaches worldwide.

In summary, the Laws of Proportions of Similar Triangles and Pythagorian Theory dictate what empirically should be observed to occur in real life pole vaulting at the take-off.

I find there is no convincing evidence to show that the predictions that follow from this theory are not verified in the practical performance of rigid or flexible pole vaulting take-offs.

I leave readers to make their own judgements.

Having established an accurate mathematically predictive basis upon which to describe the pole vault take-off foot location on the runway it remains to be demonstrated what real life pole vaulters actually do when they perform a pole vault take-off.

The take-off I functionally define as:

“The physical method used by a vaulter, whilst attached to the pole by two hands firmly gripping it, to project their body and the attached pole from the ground by a single leg propulsion technique. The propulsion technique adopted to do this should efficiently minimize loss of energy / momentum accrued during the preceding approach run and pole planting actions.
At the culmination of the propulsive projection (projection leg toe-tip breaking ground contact) the vaulter’s body and the pole should be oriented spatially and temporally in such manner the capacity of the vaulter to continue to propel and steer (drive) the total vaulter pole system is optimal in setting up and accomplishing the next sequential component of the vaulting process.”

Currently there are three types of take-off advocated as having efficacy in achieving optimum functionality in the pole vault take-off with a flexible pole.

The oldest and perhaps still the most widely used method of take-off I refer to as,

(1) The Deliberate Pole Pre-Bend Take-Off Technique. In this form of take-off the pole undergoes considerable bend induced deliberately by the vaulter before the take-off leg toe-tip breaks ground contact. Currently this is the method being successfully used by Renaud Lavillenie.

The next most widely adopted method of take-off is the “Free-Take-Off; Petrov-Bubka Model” the take-off technique currently central to the discussion in this thread I refer to as,

(2) The Free- Take-Off. In this form of take-off the pole is deliberately kept straight (recognising there is a natural bend due to the manufacturing method and the location of the centre of mass of the pole) as the vaulter attempts to reduce resistance to the forward progression of the total system during the take-off until the simultaneous pole tip impact with the rear wall of the planting box and the take-off foot toe-tip breaking ground contact. Initial pole deformation, due to impact with the rear wall, occurs whilst the vaulter is suspended from the pole. The vaulter is no longer directly influenced by the foot being attached on the ground and therefore is dependent actively and reactively (Newton’s Laws) upon the pole which is attached to the mass of the earth directly through the planting box contact.

The third and quite rarely seen, even amongst elite male and female vaulters, is what I will refer to as “The Pre-Jump Take-Off.” An extreme example of advocacy of this form of take-off is the “Air Strike System.” I will refer to the pre-jump take-off technique as,

(3) The Pre-Jump Take-Off. The pre-jump take-off has two forms. The first type is a pre-jump technique in which both the vaulter and pole are momentarily airborne before any part of the planting box has been touched by the pole tip (advocated in the Air Strike System).
In the second type of pre-jump technique the pole tip is minimally in contact with the planting box sliding towards the rear wall as the take-off toe tip breaks ground contact. The travel trajectory of the vaulter and pole is uninterrupted (there is a resisting frictional force opposing the motion direction of the pole slide, but it is quite small relative to the inertial force of the vaulter pole system) until the pole tip contacts the rear wall so the vaulter can be considered to be freely suspended from the pole until this time. The vaulter is suspended below the hand grips when the initial deformation of the pole due to rear wall impact occurs.

(Note: the vaulter can never actually be “free” at any stage in pole vaulting because of the mutual gravitational attraction force that exists between the mass of the earth and the mass of the vaulter. The same applies to the pole).

I will delimit the rest of my contribution in the discussion to only consider Free and Pre-Jump Take-Off Techniques before I can comprehensively answer Kirk’s original question.

In my drawings below two of the take-offs depicted are unarguably Free Take-Offs. The other is close to achieving this form of take-off but has to be classified as a Pole Pre Bend Take-off.

Becker Take-Off comparison.jpg (92.33 KiB) Viewed 41374 times

Careful examination of the paths of the vaulter centre of mass between touch-down, mid-stance (support), toe-tip take-off and the rate of angular displacement, about the take-off foot toe-tip, during the total ground contact phase is revealing.(The drawings were made from still frames of the videos previously cited and superimposed with respect to the takeoff foot when fully grounded).

The body postures at touch-down, mid-support, and toe-tip take-off are also informative despite the small but practically very significant kinematic differences.

These small differences have quite dramatic consequences on how, where and when the pole subsequently bends under compression forces induced by the take-off resultant linear translation force components and the centripetal force induced pole compression due to initiation of vaulter swing from the wrists joints of the lower and upper arm hand grips on the pole.

What net effective propulsive thrust the vaulter can actually achieve at the instant of toe-tip take-off is critically determined by vaulter actions during both the amortization and propulsive phases of the take-off and is particularly affected by:

(1) Horizontal distance in advance of the position of the vaulter’s centre of mass (COM) of the Take-Off foot at touch-down and the quantum of horizontal inertia generated by the approach run and plant initiation at that instant.

(2) Horizontal displacement forwards of the COM during the amortization phase of the total ground contact time as well as the amount of lowering to be decelerated and redirected during mid stance.

(3) Synchronicity of the timing and coordination of the total combined effort contribution from both arms as they complete the pole plant, the magnitude and direction of momentum transfer from the lead leg action coupled to the take-off limb hip, knee and ankle power delivery to accelerate the COM in an upward and forward direction.

Videos referred to and the drawings above provide some evidence I invite readers to consider against their own empirical experience of pole vault take-offs. Having done this, I trust that you will formulate your own hypotheses as to the effects the take-off has upon pole bending.

In my next posting I shall examine the variability possible in executing any pole vault take-off. Also I will attempt to show why the subtlety of the instruction in the Petrov-Bubka Free-Take-Off to Spring Upwards and Forwards rather than Forward and Upward produces a totally different set of dynamic consequences in the pole compression phase of the vault.

[PVstudent]

In the diagram the basic breakdown of the phases of an actual take-off is shown. The take-off commences at Touch Down and ends at the Toe Tip Takeoff as depicted in the drawing made from the still frame taken from the video see:

http://youtu.be/9YK-7dZksCM

Structure of the Jump position A.jpg (117.66 KiB) Viewed 41214 times

If the reader uses the decision tree flow diagram it is clear that the plant pole tip contact with the rear wall of the box occurred between mid-stance and toe – tip takeoff. At take-off the pole has already experienced bending with the pole chord making an angle of 34 degrees to the right horizontal as the toe tip breaks contact with the runway surface.

Decision Tree for Take-Off Recognition.jpg (76.76 KiB) Viewed 41214 times

The video is suggestive that the pole tip made contact with the planting box apron and had a short distance translation slide along it whilst it rolled in the (+ve) anticlockwise direction about a transverse (-Z to +Z) axis. The roll is a consequence of culmination of the planting arm action and the up-spring from the flat foot mid stance transition to tip-toe.

Pole tip and action in box 1.jpg (78.43 KiB) Viewed 41214 times

Video observation also shows that the direction of the vaulter’s thrust, through the take-off foot to pass through his centre of mass, caused considerable advance of the vaulter’s torso and hips in the forwards direction past the grounded take-off foot before rear wall strike by the pole tip.

Pole tip impact causes this torso and hip advance forwards to accelerate the motion about the top grip hand axis as the toe tip leaves the ground.
The vaulter is this video appears to push the pole, primarily in the upward direction, by the lower grip arm even though the elbow is flexed. Upper arm is abducted with slight external rotation as the total limb undergoes flexion about the shoulder joint.

A detailed analysis will reveal why this is a biomechanical error and will be addressed later.

The impact of the pole tip with the rear wall of the box is a critical determinant of the success or failure to integrate the pole plant with the take-off in minimizing loss of the horizontal inertia built up in the approach run and plant, especially during the propulsive phase (mid-stance to toe tip take-off) of the take-off ground contact time.

[PVstudent]

The diagram below shows possible pole tip impact conditions and types of impact that arising when completing and or failing to complete a pole plant to complete a take-off successfully.

Pole tip and possible impact conditions 1.jpg (71.87 KiB) Viewed 41203 times

The table below briefly summarises the type classification of take-offs with respect to possible pole tip impacts contacts on and against the planting box depicted in the diagram above.

Pole tip Type of Take-off Impact.jpg (103.55 KiB) Viewed 41203 times

The diagram and table summarize potential interactions that are observed in modern flexible pole use in pole vaulting. The interactions possible during the time from touch-down to toe-tip take-off are identified in the following diagram. Understanding what is happening during the 0.1 to 0.16 of a second that the take-off ground contact requires experience, the visual assistance of slow motion video and the understanding of the mechanics of impacts of deformable bodies. The time of the take-off in pole vault is about half the time of a single eye blink! The analysis that follows has been informed by the information provided by high speed video, force transducers and years of practical research and elite level coaching.

Pole tip and possible impact conditions interactions 1.jpg (68.45 KiB) Viewed 41203 times

Direct shock transmission forms of pole resisted take-off (2) are most frequently observed in those vaulters who rely on taking off “under” and being swept off the take-off foot by the shock of the impact. The reasons for this approach, in my experience, can be broadly summarized as follows:
1. Excessive speed in the approach run and backward lean into the plant to control low pole carry angle.
2. Plant started late because of the low pole carry.
3. Over step on last step.
4. Failure to complete the pole plant with the top grip hand which only gets level with the top of the head. Pelvis, spine and shoulders have to become misaligned to compensate.
5. Planting by advancing the lower grip hand forward with the elbow higher than the grip on the pole and excessive elbow extension to move the pole too far out in front of the lower arm shoulder. The pole tip is advancing with greater linear speed than the vaulter when it strikes the rear wall some height above the deepest part of the planting box.
6. Knowledge of how impact conditions influence bending the pole (especially when length of top hand grip along the pole is large and the pole is relatively stiff) is deficient or is simply unknown so the vaulter has to rely on speed of pole impact to make a take-off.
7. This is the method by which the vaulter was taught when beginning pole vault.

This is not efficient, nor is it a technique that allows much potential for the future development of the vaulter. It creates too many “blind alleys” and eventually kills any prospect for further progress in performance achievement. This is often the type of take-off used by novice boys and girls who are big and strong for their age group, who can, in the beginning dominate and win competitions, simply using their speed and power to “muscle” the vault.

Winners in this category grin at first but weep later when they stagnate and are unable to overcome the ingrained technique errors produced. That is if they are lucky enough to have survived the many occasions on which they will have been rejected by the pole!

[PVstudent]

Pole resisted take-off is in widespread use at all levels of competitive pole vaulting.

It is widely taught and practiced, in the USA and France in particular, and has enabled many 21st century pole vaulters to reach elite international status. Indeed Jennifer Suhr and Renaud Lavillenie are superb pole vaulters who currently use this take-off technique.
http://youtu.be/r9s3I2FuOaQ
http://youtu.be/RtZH3Q19w4I

Pole resisted take-off.jpg (92.03 KiB) Viewed 41175 times

There are many advantages to the technique, especially for smaller stature, low body mass acrobatic males and powerfully built females (for example Yarisley Silva), who because of their gymnastic agility, aerial awareness and capacity to fearlessly exploit the “early” recoil of highly flexible poles (relatively low stiffness for the grip lengths used) to achieve success.

http://youtu.be/qxmhxpvJHqM

The technique fundamentally requires the power employed to be high in the velocity component per unit body mass supplied by the musculature of the vaulter.

The method may better suit the power weight ratio advantaged smaller stature vaulters with their limbs having lower moment of inertia characteristics (ie they have advantages for initial swing speed, tuck and shoot to exploit a large amplitude phase 1 pole bend with early recoil (from maximum pole bend).

Evolution of the “Free-Take-off” and technique advantages conferred to tall vaulters.

Taller vaulters generally possess proportionally longer limb lengths and thus greater limb segmental moments of inertia. This requires greater force output per unit of muscle mass to overcome initial limb inertias for the taller vaulter to produce change in limb motion direction when the limbs are fully extended.

However, because of these longer limbs the taller vaulter has the advantage once the limb is moving of being able to achieve much greater tangential velocity in the limb distal segment (end furthest away from the joint axis) end due to their longer radii from the joint axes (Tangential velocity = Radial Velocity( radians/sec ) X length of radius (metres)).

Tall pole vaulters must also be powerful ((Force x velocity) or (force x (displacement/time)) to be proficient pole vaulters. Thus they have to rely on the force (magnitude) and displacement components of their power output and will take somewhat longer to do the work. They must therefore create the space and the time to be able to exploit their anthropometric and anatomical advantages in their take-off technique.

Pre-bending the pole by being “under” and or lacking upspring in the take-off is clearly disadvantageous to taller vaulters who also possess more body mass that shorter vaulters. Nor do taller vaulters enjoy the same power to weight ratio advantage of the smaller stature vaulter.

Torques pole tip and top hand 1.jpg (107.49 KiB) Viewed 41175 times

The technique of the take-off for taller vaulters requires them to have a bigger space and increased time period in which to generate upspring to take advantage of their greater potential energy (mgh) due to their tip-toe COM (centre of mass) position above the runway on take-off.

Taller vaulters can, if their total body rotational inertia is overcome via the torque applied by the pole contact with the rear wall of the box when the vaulter is suspended from both hands gripping the pole, exploit this by immediately maintaining their lower grip arm resistance to the initial pole bend ie they should pull against the pole the instant the toe-tip leaves the ground.
The pull is executed by the entire lower grip arm exerting a powerful active ECCENTRIC muscle action. The action is a reversed muscle action in that the eccentric muscle action pulls across the shoulder joint on to the trunk via the scapula and the thoracic attachments of the lower portions of latissimus dorsi muscle.

Since the pole is moving in an upward and forward direction away from the vaulter the eccentric muscle resistance, if timed correctly and supplied by the shoulder joint and girdle of the lower grip arm side of the vaulter, helps to provide total vaulter linear displacement horizontally about the top hand. At the same time the range (amplitude) of trail leg swing motion is increased.

Also, since the vaulter’s rotation inertia about the top hand has been overcome by the torque provided by the shock of impact transmitted instantaneously at pole tip impact, the simultaneously lower arm “pull” and “whip-like” trail leg swing muscle power application generates both penetrative drive and very large centripetal force against the pole.

This coordinative synergy also maintains a lower total system moment of inertia about the pole tip horizontal transverse axis and thus helps maintain pole chord rotational speed in the direction toward the transverse vertical plane of the cross-bar.

Pole supplied torque acting through the hand grips exploits the tall vaulter’s leverage and tangential velocity generation advantages to drive (guide) the total system (vaulter plus pole) without interruption by the vaulter continuously generating muscular power until pole release.

structure of the take-off 2.jpg (113.42 KiB) Viewed 41175 times

If the vaulter’s foot is not in ground contact when the pole –tip strikes the rear wall taller vaulters can also exploit their learned ability to adjust both linear and rotational whole body inertia by controlling their chest, anterior abdominal wall, shoulder and shoulder girdle muscle-joint reaction torques to the torque exerted on them by the pole impact.

When properly timed the active eccentric action of these muscle joint complexes allows the horizontal component of the resultant thrust force (horizontal inertia) at take-off to displace the suspended vaulter’s body forward past the pole impact resisted forward progression of the hands gripping the pole.

The vaulter adjusts muscle joint tension around the upper anterior chest wall, both shoulder joints and the shoulder girdle to allow the horizontal inertial component of the resultant force acting through the COM to rapidly displace the vaulter forwards relative to impact reaction force transmitted from the pole through the firm hand grips on the pole.

This action when properly executed adds linear horizontal travel (penetration) to the total system COM before the vaulter’s weight significantly contributes to bending the pole. It also allows the vaulter more amplitude through which to add take-off (trail leg) swing prior to maximum pole bend in the first phase of pole support.

(Note: This is not done consciously on the part of the trained vaulter but requires quite deliberate focused efforts during the early learning phases of technique acquisition).

Also the taller vaulter is better able to exploit the increase in potential energy due to COM position height and the Increased pole ground angle that their closer horizontal position to the rear wall of the box at take –off, if the verticality of their jump from the ground is increased.

The straighter the pole and the higher the pole ground angle are at rear wall impact the less the horizontal linear inertia of the total system is impeded by the impact of the pole tip. This is because the rotational angle of the pole chord is closer to vertical, more closely aligned to the longitudinal centre line of the pole and the pole is rolling on the apron of the planting box as its slides and collides with the rear wall.

(The amount and rate of pole tip roll at the instant of rear wall impact along with the pole chord ground angle and resultant take-off force acting through the vaulter’s COM plus the degree of vaulters “rigidity” at this instant determine the outcome of the collision. Pole deformation/ restitution characteristics, the type, shape, wear and the material properties of the pole tip are also contributing factors to impact shock absorption and transmission).

This is why , I believe, shorter vaulters as they move to stiffer poles at greater grip lengths, technically change their technique towards more verticality in the take-off upspring and become less dependent on deliberately pre-bending the pole by always being “under”. Recent vaults by Renaud Lavillenie and Yarisley Silva previously cited, I belief have demonstrated this evolutionary change to their take-off technique.

When the vaulter’s take-off foot still retains a firm contact on the ground as the pole tip impacts the rear wall the linear motion of the hands is instantly retarded relative to the rest of the vaulter’s body. Due to large horizontal inertia at the vaulter’s COM, the pelvis, abdomen and hips continue their forward linear displacement towards the transverse vertical plane of the rear wall of the planting box relative to the grounded and fixed take-off foot and the hand grips on the pole.

This diminishes the effectiveness of the vaulter’s upspring attempt, reduces potential energy gain from height of the COM at take-off, reduces pole ground angle at take-off, causes relatively large pole bend at take-off and consequently reduces the effective capacity of the vaulter to generate pole penetration.

The penetration energy being dissipated as pre-bend in the pole results in reduced horizontal forward displacement travel of the total system COM by the time maximum pole bend is reached and pole recoil starts.

In effect the vaulter is further back from the vertical plane of the pole tip located in the box and will have had less amplitude of angular displacement to swing through, as well as less time in which to generate large centripetal forces to induce additional pole bend prior to pole recoil.

It is my experience that vaulters who experience this difficulty when using the pre-bend take-off, compensate by choosing higher stiffness number rating poles (more compliant the higher the rating number) and thus gain more pole bend in phase 1 of the pole support.

As a consequence they lose out in the ability of the pole to respond fast and forcefully enough in phase 2 (recoil) as well as have lower projection velocity at lower projection angles with insufficient penetration at pole release.

In addition the standards are often set closer to the rear wall of the planting box which simply exacerbates the problem.

[PVstudent]

A Case Study of How Attempting to Produce a “Free-Takeoff" Affects the Rotational Kinetics of the Take-off Outcomes (Part A).

What follows shows how attempting a “Free – Take-Off,” in which the vaulter is more upright whilst trying to maintain body core area muscular fixation at pole tip impact, combats many of the problems associated with the pole bend resisted take-off technique.

The video still frames below show that the kinematic differences between jumps can be very slight. Subtlety of these small kinematic differences is revealed by looking carefully at the relatively large effects they have on the kinetics of rotation outcomes of pole vault take-off technique.

Take-off kinematic slight differences.jpg (73.43 KiB) Viewed 41172 times

The diagram below attempts to make clear what is meant by the tangential vaulter generated force that produces a torque about the pole tip transverse axis located in the planting box and an oppositely directed torque about the transverse axis through the wrist of the top grip hand. The diagram deliberately does not show the inertial, weight and frictional forces that are also present. This has been done to clarify the concept of the torques created by the angle of attack thrust force generated by the vaulter during the take-off.

Torques pole tip and top hand 1.jpg (107.49 KiB) Viewed 41172 times

What should also be noted is that as the angle of attack (theta) is increased the perpendicular distance (d1) from the action line of the thrust force through the vaulter’s centre of mass and the pole tip also increases in length. The same thrust force magnitude, but exerted at a higher more vertical angle of attack, will therefore generate more torque about the pole tip transverse axis.

The contrary effect occurs with the torque applied about the vaulter’s top hand grip. As the angle of attack becomes more vertical, perpendicular distance (d2) shortens and decreases the torque produced by the thrust force magnitude which remained constant.

continued next post ...

[PVstudent]

A Case Study of How Attempting to Produce a “Free-Takeoff Affects the Rotational Kinetics of the Take-off Outcomes (Part B).


The diagrams that follow are based on a real life vaulter and actual video recorded vaults.

Position A of vaulter: http://youtu.be/9YK-7dZksCM

Position B of vaulter: http://youtu.be/TK_rAC0gjXk

The effect of the vaulter total body angle of attack average ground reaction force thrust and verticality of postural alignment has on rotation about the pole tip and top hand axes at the instant to toe tip take-off are shown for position A and position B derived from still images of the take-off.

Torques pole tip and top hand 2.jpg (88.8 KiB) Viewed 41170 times

The diagrams are not truly exact nor are forces exactly to scale. However, the force magnitude representations have been kept constant at each position. Only the angle of attack has been changed between Position A and Position B.

Because the angle of attack increases in position B the angle of projection (gamma) of the COM in Position B accordingly must also show a slight proportional increase.

(Force magnitudes are kept constant for positions A and B to illustrate the effect the verticality and rigidity of the take-off postural configuration has on the total system rotation about the pole tip and the local rotation of the vaulter with respect to the top grip hand axis. It was quite impossible to use accurately scaled force representation of the relatively small friction force due to pole slide or even the weight force of the pole in the diagrams. When I address the pre-jump take-off I will present actual measurements of take-off ground reaction forces acting on the vaulter and reaction forces from the planting box acting through the pole tip!).

Torques pole tip and top hand 4.jpg (92.99 KiB) Viewed 41170 times

Note in the diagram above, showing the slightly more vertical upright posture in postural alignment in position B, that the moment arm (d1) has increased to produce greater anticlockwise (+ve) torque around the pole tip axis. Also shown is the relatively smaller reduction in (d2) the moment arm length about the top grip hand axis.

Thus the more vertical body alignment produces more pole rotation towards the transverse vertical plane of the cross-bar and less rotation about the top hand grip merely by increasing the applied thrust angle by a small amount (delta). The slight increase in the elevation of the vaulter COM above the ground gives the vaulter additional gravitational potential energy.

Torques pole tip and top hand 5.jpg (84.96 KiB) Viewed 41170 times

The action lines of the resultant force acting through the centre of mass of the vaulter in position A (line A-A) and for position B (line B-B) which was held constant in magnitude shows the very large effect this same force has on the torque generated to produce pole plus vaulter rotation about the pole tip axis at take-off.

Since the pole ground angle has also increased for the vaulter in position B there is less angular displacement (angle beta) about the pole tip required to reach the transverse vertical plane through the pole tip.

Initial potential energy at takeoff has also increased in position B.

The diagrams above have shown that the Petrov / Bubka Model instruction to take-off UPWARD and FORWARD, changes not only the pole ground angle, but how the torques developed rotate the total system as well as the vaulter suspended from the pole.

It still remains to visit the pre-jump take-off.

The next post on the topic will present objective data to show that the pre-jump, as yet unexplored, does exist as a take-off possibility. Why the pre-jump is rarely seen, has not been easy to record in elite competition when it has occurred, as well as whether the pre-jump is a viable corrective means to ultimately achieve a “Free Take-Off" will be discussed.

[PVstudent]

The 30 year old enigma of the pre-jump being a fictitious imagining of a deranged coache's mind still persists and continues to be regarded as merely hypothetical and of no consequence should any vaulter be rash enough to attempt such an heretical act.

For example, David Bussabarger PVP: Mon Sep 10, 2012 7:16 pm writes:

“I am against the pre jump because it is tantamount to jumping on the pole. Also, based on a good deal of visual research, I could not find any clear evidence of an elite vaulter (this includes all the 6m. vaulters) successfully employing pre jump technique. In other words I could not find any empirical evidence that shows that the pre jump actually provides any benifit to the vaulter. It is, from what I can tell, an idealized, hypothetical construct.”

1. The pre-jump take-off does it exist? 2. Has the pre-jump been used in Elite competition by Elite Pole Vaulters? 3. Is pre-jump take-off an idealized, hypothetical construct?

The short answers are:
1. Yes it does exist and
2. Yes it has been used in elite competitions and
3. No it is definitely not an idealized hypothetical construct.

Some of the evidence for my answers to Mr Bussabarger’s bold but unfortunate misinformation follows.

Maurice Houvion (1983) shows pre-jump drills in his video that predate Vitaly Petrov’s seminal Free-Take-off and Pre-Jump presentation in Birmingham England in 1985.

http://youtu.be/9_hzB33V8wE
http://youtu.be/SS1mctHgeXE

Jean Claude Perrin made this statement (1984)

“The European vaulters are actually jumping into the takeoff in much the same fashion as long jumpers. They are also taking off about 30cm further back of what has been regarded as the ideal spot vertically below the top hand.
As the result of the changed takeoff action the vaulters are actually in the air, or off the ground, before the pole hits the back of the box. During this phase the shoulders are ahead of the hips, accomplished by a short last stride.”

(From: Modern Athlete and Coach, (Vol 27; Issue No 2)

Sergei Bubka gave this anecdotal evidence in regard to the Petrov – Bubka Free Take-off Model of the Pole Vault Take-off;

“Q. What is your point of view on the advantages and importance of the free take off?
A. In pole vaulting the crucial factor is how to transfer energy to the pole, through the complete body of the vaulter; the arms, shoulders, hip, back and legs. But, if the pole begins to bend while the vaulter is yet on the ground, it is impossible to transfer the energy, all the energy is lost and goes to the box. The point is how to achieve this? The free take off is a very short period of time, we can say no more than hundreds of a second, going from the end of the take off and the moment in which the tip of the pole reaches the end of the box(ie a Pre-Jump Take-Off). But this very short time makes a big difference that allows the competitor to greatly improve the results. When we begin to bend the pole, while being on the ground, we can see an arched position of the body, on the other hand, if we perform a free take off we can feel the pushing action of the whole body, and we can transfer the speed of the run up and take off.
Additionally, we can increase the angle between the pole and the ground in the moment of taking off. This angle is a very important technical factor, because the bigger this angle the better the result.
But this angle must be achieved with a complete extension of the body, and mainly, keeping that short difference between the full extension of the body and the tip of the pole reaching the end of the box.It is a crucial factor, but at the same time, it is not easy to achieve. During my career, I was able to do it sometimes.”
(The parentheses are mine).

Sergei Bubka (2002). Round Table With SERGEY BUBKA July 20-21 Kingston, Jamaica.
Source : http://www.mansfieldathletics.com/pole_ ... rview.html‎

The video clip below is indisputable empirical evidence that, on at least one occasion, Sergei Bubka actually performed a pre-jump take-off under competition conditions. This suggests, to me, that I can reasonably rely upon Sergei Bubka’s anecdotal evidence as having some validity because it is supported by empirical fact!

http://youtu.be/y9Q4rL0PC-s

According to Dr. Nick Linthorne (previously a pre-jump skeptic!):

“A simple test for determining the instant when the pole strikes the back of the box is to look at the position of the upper hand relative the vaulter's head. During the final stride of the pole plant almost all elite vaulters extend their upper hand directly above their head. When the pole strikes the back of the box, the vaulter is unable to completely counteract the force exerted on his arms by the pole, and so the vaulter's arm is forced back behind his head. The instant the pole strikes the box is therefore the time when the upper hand first begins to move backward relative to the vaulter's head.”

In the Bubka video there is little indication of the top grip arm being driven backward by the pole tip impact reaction force until his take-off toe tip is off the run-way.

According to Nick’s web site a pole vaulter who gets airborne before the pole strikes the back of the take-off box is Dmitry Markov at the 2001 World Championships in Edmonton.

Dmitri Markov Free and Pre-Jump Take-off.jpg (100.41 KiB) Viewed 41108 times

http://youtu.be/oFf69dJ-Elo (5.95m Jump)
http://youtu.be/nf-xO3lCOks (6.05m Jump)

Dmitri Markov recorded the highest ever jump in any IAAF World Championship pole vault final to date. Dmitri’s 5.95m penultimate clearance was indisputably a pre-jump take-off and his winning 6.05m jump definitely a “Free take-off and arguably a pre-jump!”

Below are photographs that show a pre-jump takeoff being used by female vaulters in a competition context.

Pre - jump Take-off 4.jpg (73.2 KiB) Viewed 41108 times

Tatyana Polnova is recorded in the sequence shown below to pre-jump at take-off in elite competition. Tatyana is ranked 10th on the IAAF All Time Women’s Pole Vault Athlete List with a personal best height of 4.78m.

Polnova Pre-Jump 2.jpg (48.71 KiB) Viewed 41108 times

The sequence of images recorded above shows Tatyana Polnova executing a pre-jump in competition.

From both anecdotal sources, as well as empirical evidence the pre-jump take-off is demonstrated NOT to be an “idealized, hypothetical construct”!

I have also shown the pre-jump to have been performed by some male and female elite pole vaulters and proven by them to be effective in contributing to successful Elite Level (World Elite) pole vaulting performance.

[tsorenson]

PV Student,

I am enjoying your extremely detailed posts. In my case, you are preaching to the choir, but it is still nice to see all the "empirical evidence" laid out for everyone. Keep up the good work! As you pointed out, the takeoff point is largely dependent on the action of the vaulter; i.e. your step does not necessarily get you the benefits of a free takeoff.

I especially enjoyed the old Houvion films, which I had not seen before. Keep 'em coming!

Cheers,
Tom

[PVstudent]

Pole vault Pre-jump recorded in competition and training research. Part A.

“Remembrance of things past is not necessarily the remembrance of things as they were.”
― Marcel Proust.

Renaud Lavillenie 6.02m Pre-Bend Pole Resisted Take-Off.jpg (56.72 KiB) Viewed 41033 times

“When we begin to bend the pole, while being on the ground, we can see an arched position of the body, on the other hand, if we perform a free take off we can feel the pushing action of the whole body, and we can transfer the speed of the run up and take off.”
Sergei Bubka (2002). Round Table With SERGEY BUBKA July 20-21 Kingston, Jamaica.

Renaud Lavillenie, in the take-off shown above, demonstrates empirically that Bubka’s statement accurately describes a pre-bend pole resisted take-off.

I suspect that Bubka may be equally accurate in his feeling (kinaesthetic) description “of a free – take-off ...”we can feel the pushing action of the whole body, and we can transfer the speed of the run-up and take-off”. However, it is impossible for anyone else to know what Bubka’s kinaesthestic sensations actually feel like! We can only guess.

However, it is possible to objectively measure the extent to which Bubka is actually able to “... transfer the speed of the run up and take-off.”

The reported kinaesthetic evidence revealed by Bubka can be qualitatively assessed by matching his description against our own movement experience to infer what a free take-off might feel like if we were able to execute such a take-off. This would be, at best, a purely subjective personal judgement of our belief as to the accuracy of our guess about what another person feels. The confidence in our belief can only be indirectly determined by making comparative inferences that rely on attribution of a personal kinaesthetic sensation as being the same as those experienced by another person in performing the same task. The truth or otherwise of shared “sameness” of attributed kinaesthetic sensations is unverifiable.

Some elite pole vault athletes and coaches of the Pre-Bubka fibreglass flexible pole vault era when contributing to PVP would do well (IMHO) to note Proust’s admonition in regard to memory especially kinaesthetic memory.

Indeed, everyone is highly fallible when reliant upon the veracity of recall of kinaesthetic memory traces of personal performances made 30 or 40 years ago. Even our visual recall, of our very recent real life witnessing of the pole vaulting techniques of others, requires a healthy degree of scepticism as to accuracy and verifiability of the witness claims we might make.

Objective recording and measurement of pole vaulting parameters obtained by means of film and video has provided a large body of relatively objective measurements of kinematic data characterising pole vaulting using flexible poles.

Kinetic data obtained in training and in competition by valid measurement techniques are relative sparse regarding the dynamics of the take-off.

What scientific observation and analysis of” Free Take-Offs” and in particular the “Pre-Jump Take-Offs” have been reported?

Empirical evidence obtained by scientific analysis of observations and measurement techniques using kinematic analysis shows the pre-jump to have been practically implemented at the highest competitive level pole vault competitions namely at IAAF Junior and Senior World Championships!

The first scientifically recorded measurement of a pre-jump being used in an elite competition was made in 1986 at the 1st IAAF World Junior Championship, Athens, for the vault by Delko Lesov of Bulgaria (Silver Medal) with a jump of 5.40 metres. The pre-jump was recorded by an Official IAAF Biomechanics Research Team that used LOCAM cine film cameras operating at 100 frames per second. Researchers then carried out 3D kinematic analyses of selected parameters measured from the images they had obtained.

http://youtu.be/VLnrZazlqyA

In the 2005,Helsinki, World Athletics Championships the IAAF Biomechanics Research Team employed digital video recording of the vaulter motion whilst simultaneously recording measures of the reaction forces from an instrumented planting box during the Men and Women’s Pole Vault Final.

( Falk Schade .,1Gert-Peter Brüggemann., Juha Isolehto., Paavo Komi., 2 Adamantios Arampatzis (2005) POLE VAULT AT THE WORLD CHAMPIONSHIPS IN ATHLETICS, HELSINKI 2005, Final Report.

Force measurement Isibayeva 5.02m World Record.jpg (48.46 KiB) Viewed 41033 times

The force recording is that obtained from Yelena Isinbayeva’s 5.02m World Record Jump. Readers may be interested to see a video recording taken of that particular jump.

http://youtu.be/Ml_nBlLLiRg

No instance of a pre-jump was recorded for either the male of female finalists at that championship.

[PVstudent]

Pole vault Pre-jump recorded in competition and training research. Part B

Falk Schade and A Arampatzis (2012) published a study of German pole vaulters performing the Jagodin Take-Off exercise.

The figure shown below is taken from that study.

Forces for Jagodins.jpg (43.32 KiB) Viewed 41029 times

The reaction forces acting via the vaulter’s take-off foot show a long duration “braking” force for more than 75% of the take-off foot contact time. It also shows that the pole began to offer resistance, due to pole tip impact with the rear wall of the planting box, within the first 1/3 of the ground contact time.

That is to say the pole tip must have struck the rear wall of the planting box during the amortization phase of ground contact with the take-off foot “fully grounded” (ie the vaulter was making full foot contact against the runway surface when the pole tip struck the rear wall of the planting box).

Consequently in this example the vaulter MUST have used a Pre – Bend Pole Resisting type take-off during the remaining take-off ground contact time ( refer to my previously provided take-off decision tree diagram and take-off classification table).

The combination of long duration and relatively large “braking” forces counteracting forward horizontal momentum due to the ground contact suggests that, in this case, the vaulter’s “core – body section- lower torso, abdomen and pelvic girdle” would have advanced towards the vertical plane of the cross –bar well ahead of the top arm grip and take-off foot ground contact locations.

Since the time interval between take-off foot touchdown and pole tip impacting the rear wall is so short the shock of the impact (“jerk transmission”) will instantaneously retard any horizontally forward progression of both hands gripping the pole.

As a consequence of this happening in the amortization phase of the ground contact with the vaulter body core region continuing in forward motion due to inertia, there will be a tendency for the top hand grip to pull downward against the pole and for the flexed, but “braced,” lower grip arm to be forced upwards against the pole.

A free take take-off, even though the take-off foot is perfectly located on the runway directly underneath the location of the top hand grip, is impossible when the plant is prematurely completed as occurred in this case.

Vaulters committing this technical error will often report that they are “actively pushing the pole up in the take-off and pressing out chasing the bend in the pole with the lower arm!”

I would expect (only my opinion) their reports would be verified as correct by an experienced elite pole vault coach observing the Jagodin exercise attempt recorded by video and force transducers for the particular vaulter in the particular example reported by Schade and Arampatzis (2012).

However, it is clear to me, that the primary functional objective of the Jagodin Exercise to jump upward and minimize the pre bending of the pole by the up-spring action to accelerate the pole chord towards the vertical plane of the crossbar is totally negated when an early plant pre-bend pole resisted take-off is used.

The researchers did not appear to have fully apprehended the significance of this KEY coaching purpose to be achieved in performing a Jagodin Pole Vault Take-off Exercise (See also CoachJVinson’s critique on PVP).

This take-off, as recorded by this athlete in the Jagodin Exercise has to be regarded as failing to achieve the primary functional objective and mechanical principle of all pole vault take-offs, namely minimizing energy / momentum losses during the take-off ground contact phase.

(Note: Repetition of a `Dead End Technique’ decreases the rate of improvement that can be made and increases the effort required to make even the most minor of desired technical change. The technique reported above is in my view a waste of an elite vaulter’s time and has a high probability of retarding progress and the potential to cause performance to plateau permanently).

The accompanying stick figures also confirmed that the Jagodin Exercise has simply been performed very badly on this attempt.

From my coaching perspective, all this performance of the exercise achieved was reinforcement to learning a biomechanically and anatomically contraindicated take-off. By performing the Jagodin in this way the vaulter concerned is merely deeply “ingraining” a technical flaw that limits possible realizable vaulting potential.

(Note: Also consider the acute and chronic stress loading on the vertebral processes and apophyseal joints created by the inertial induced lumbar hyperextension, lateral flexion and transverse plane rotation that such a take-off technique imposes on the athlete. This needs to be very carefully considered when working with younger athletes and very powerful mature female vaulters of slender somatotype.

The way in which the Jagodin Exercise has been performed, as revealed by the take-off ground and box pole tip reaction forces produced by this particular vaulter, from a biomechanical perspective:
• impedes the effectiveness of forward penetration of the total system centre of mass,
• reduces the angular velocity of the pole chord at take-off,
• causes very early pole recoil,
• reduces the amplitude of the trail leg swing,
• prevents the trail leg swing from keeping the total system moment of inertia low about the pole tip axis
• exacerbates the problem of “blocking” with the stiffly “braced” lower arm.

In effect the technical elements the Jagodin Exercise purports to teach and reinforce are being entirely negated by this athlete. The researchers appeared to be blissfully unaware of any of these potential unsafe and hazardous outcomes caused by performing such a technically deficient pole vault take-off!)

In an excellent critique of this study contributed by CoachJVinson on PVP the interpretation of the data by the authors was shown to lack objectivity in addition to other problems he identified and discussed.

Instead of falsifying the Petrov/Bubka Free Take-Off hypothesis, as the authors claimed, I contend that they produced:

(a) experimental data support and beautifully illustrate Netwon’s Law of Motion (the Action -Reaction Principle in particular)

(b) data that can be more fairly interpreted as substantiating the desirability of achieving minimal pole resistance prior to take-off as an effective means of improving the “mechanical efficiency” as well as the effectiveness of the take-off in the Jagodin Exercise performance outcome.

The graph below shows the planting box reaction forces recorded by a female Australian vaulter (Commonwealth Games, Bronze Medal) during training at the South Australian Institute of Sport (SASI) performing a pre-bend pole resisted take-off technique for an actual vault to clear a bungy cord bar set at 4.0m.

Force measurement Isibayeva 5.02m World Record 3.jpg (99.1 KiB) Viewed 41029 times

The pattern of the graphical representation of the forces obtained in my study produced by this female vaulter closely resembles that obtained in Helsinki for Isinbayeva (see Inset and previous graph).

There is one feature of distinct difference, marked by a black dot placed on the planting box vertical reaction force graph produced by the Australian vaulter. In this vaulter’s case the pole bounced off the planting box apron and struck the rear wall some distance above the deepest point.

This produced a torque on the force transducer that momentarily registered a negative directed impact reaction force from the box (ie the force transducer was momentarily subjected to an upward un-weighting force). The pole then slipped down the rear wall and a positively (upward) directed vertical reaction force from the planting box was recorded. This would have occurred initially if the pole tip had struck the rear wall in the deepest location possible.

As is shown in the vertical reaction force time graph for the Isinbayeva data a small positive force spike can be seen when the pole tip strikes the rear wall of the planting box at its deepest point.

Magnitudes of the forces and the temporal characteristic of the vaulters in the pole support phases are remarkably similar.

The fact that different researchers, different equipment and slightly different methodologies was used to obtain these comparative data for two different vaulters obtained in a training versus World Championship context, I suggest, gives strong support as to the objectivity, validity and the replication of results capability of the system I used to record the pole vault take-off and pole support phase reaction forces.

[PVstudent]

Pole vault Pre-jump recorded in competition and training research. Part C

Why is the “Free-Take-Off” and especially “a Pre-Jump” take-off so difficult to verify by objective, valid scientific observation methods?

Firstly, scientists, particularly research biomechanists, often know very little about the technical performance demands on a pole vault athlete.

Secondly, pole vault opinion is available in abundance whilst empirical facts are few, and factual information concerning technique that is available is not readily accessible to most scientists or pole vault coaches.

This presents the scientist with a “Janus” type quandary.

One face of the problem for the scientist is that knowing very little is advantageous in terms of the objectivity and lack of bias the scientist can bring to the study of the problem areas. On the other the scientist’s lack of fundamental knowledge of the event and the demands it makes on the athlete often results in enormous wastage of time and resources whilst the scientist discovers what elite coaches already know and take for granted and / or has been abandoned as being irrelevant or impractical to apply in the real world of training and competition.

On the other face of the issue, before they can acquire sufficient wisdom to usefully refine and research relevant questions pertinent to establishing new knowledge applicable to pole vaulting, the scientists needs to become sufficiently educated in pole vault specific knowledge based on empirical facts rather than rely on coach opinion and their own well intentioned guesswork which is often wrong or misguided.

The effort required of the scientist to overcome these aspect of the problem:
1 requires passionate interest and long term time investment for little or no pay off other than personal satisfaction and enjoyment,
2 recognition and acceptance that there will be little recognition as to the value of “sports?” applied research within the academy of the scientists for the effort expended,
3 persistence in lobbying to obtain meagre ,if any money at all is potentially available, study funding necessary to carry out the observational level studies that are necessary precursors to truly experimental research
4 neglecting some of the demands of the scientists “day job” to spend time on the unfunded research and to clandestinely use the day job facilities to do the science investigation with lab equipment downtime
5 provide hard earned professional scientific expertise for “free” because it will help the sport for which little or no funding exists
6 suspicion and/or hostility many vaulters and coaches display when questioned about “why” they do the things they do.

Most scientists need these additional problems like they need a “bullet to the head”!

Why then should a real scientist get engaged in the murky, messy world of pole vault?

I believe it boils down to the scientist having their natural and trained curiosity piqued or frustrated to the point where they feel they “have to know how and why it works.” That is my personal reason for sharing what I think I understand about pole vault take-off technique with PVP readers. It is done in the hope that I will find out where I am wrong and where my understanding is confirmed as well as trying to get the science underpinning the art of pole vaulting better understood.

As a coach who has worked with World Class Elite Vaulters I am very aware that whilst perfection is always strived for, the single element that is rarely performed to perfection is the take-off.

A pre-jump in which by definition “there is a very short period (ranging from a millisecond to some hundredths of a second) of elapsed time between the take-off toe tip breaking ground contact and the pole tip striking the rear wall of the planting box”, is, according to the laws of probability and associated degrees of freedom of variability inherent in any pole vault take-off, a rare event.

pre-Jump 15.jpg (56.71 KiB) Viewed 41008 times

Also, since the most widely available visual recording devices using modern video recording techniques usually have nominal recording speeds of 24, 25, 30 frames per second (48, 50 and 60 fields per second) the recording speeds are too slow to decisively differentiate with the precision necessary to confidently assess what is or is not a Free or a Pre-Jump Take-off.

To be assured that the toe tip of the take-off foot is off the ground and hence ground reaction force is no longer exerted directly upon the vaulter’s body via the take-off leg and the pole tip yet to strike the rear wall of the planting box, a measuring devices with sufficient time bandwidth to accurately record in millisecond units for a duration of at least 2000 milliseconds (1millisecond to 2.0 seconds) range is required. Also visual recorded images need accurate synchronization with the take-off and pole tip impact measuring instrument force registration and recording.

pre-Jump 14.jpg (65.77 KiB) Viewed 41008 times

I have, by means of such a recording system, studied pole vault take-offs performed by vaulters ranging in expertise from a female Olympic Silver Medalist, World Championship Bronze Medalist, a male Olympic Games and World Championship finalist, Commonwealth Games Bronze Medallist, Junior National Champions and State Representatives at the South Australian Sports Institute (SASI).

The force time graph shown below is based on data gathered by the system shows that a pre-jump was performed in attempt 1147 by vaulter PSJ who had a personal best jump clearance of 5.40 metres.

Pre-Jump 16.jpg (100.6 KiB) Viewed 41008 times

Quite unlike the Schade & Arampatzis (2012) study of the Jagoding Take-off, the vaulter is airborne for about 45 milliseconds as the pole tip slides along the apron of the pole planting box before collision with the rear wall occurs.

This is just over ¼ second or 6.7% of the time it takes for the blink of a human eye!

Because the pre – jump duration is a very short interval of time, approximately the time required for 1 picture frame of video to be recorded using 25 pictures per second rate, an even shorter duration pre-jump could not be reliably detected.
The research showed that using an individual video image field of 0.02 second duration has too much uncertainty to be reliable in detecting the difference between a “Free Take-Off and a “Pre –Jump Take – Off.

It is no surprise therefore why most observers have been unable to detect where, when or if a pre-jump occurs when carefully observing available video images, recorded at normal pictures per second (pps) rate of any pole vault take-off.

(The probability of a pre-jump occurring is relatively very low given the variability inherent in the pole plant and take-off elements within any pole vault performance sequence).

Viewing real life pole vault take-off and detecting a pre-jump take-off in real time by the naked eye is virtually impossible to perceive if the viewer does not understand the concept and at the same time holds the belief a pre-jump cannot provide any safety or performance advantage to a vaulter.

The event is so fast, it is less than one visual reaction time and about 1/10th of the time required for the blink of an eye. Not knowing what to look for and/or being unsure of the existence of pre jumps simply increases the uncertainty and complexity of the visual recognition response time.

So if you don’t know what you are trying to detect and biased about the possibility of the phenomenon actually being possible a properly executed pre –jump will be almost undetectable to the viewer under these circumstances.

[PVstudent]

A case study of the data from a male vaulter who consistently used a pre-jump take-off in training pole vault jumps over a 5.00m height “Bungy” soft bar is presented for the first time here on PVP.

Some video footage of the jumps recorded and measured using synchronised video, electronic timing gates, LAVEG to provide real time approach run displacement / velocity, a take-off force platform embedded in the runway and the planting box instrumented to record in three orthogonal dimensions the forces impressed upon it by the pole. A soft cross bar (bungee) set to 5.00m was used throughout the training session with uprights located 80cms from the rear wall of the planting box.

The force time graph for another pre-jump take-off by the PSJ is shown below. The criterion used to decide the toe tip take-off occurred was the return of the vertical ground reaction force to zero newtons. The decision was accurate to within a +/- 20 Netwons of force due to the very large force range being recorded and the lowest sensitivity of the transducer at which noise in the output masked the output signal.

The criterion used to decide the instant of pole tip rear wall collision was very easy to apply (see graph below). When impact occurred there was an instantaneous sudden increase in the magnitude of the output signals from all three force transducers of the instrumented pole planting box.

In producing the force time graphs it was difficult to be quite as precise due to pixilation and drawing line thickness limitations.

Pre-Jump 12.jpg (56.07 KiB) Viewed 40972 times

In the jump, PSJ, 21st May 2000 Number 1135 the pole tip made contact with the apron of the box 30 milliseconds before the take-off toe tip broke ground contact. PSJ was in the air with the pole tip sliding in the planting box for 40 milliseconds beforethe pole tip impacted with the rear wall of the box.

Thus there would be just 3 complete video image fields possible on video play back where it would be possible to check whether the toe tip had broken contact with the ground.

Without the information provided by the reaction forces from the pole planting box it is highly uncertain whether this Pre-Jump would have been identified at all by observing the video recording.

The position of the rear wall of the planting box is usually obscured when the vault is filmed at an orthogonal or oblique angle to the centre vertical plane in the fore-aft direction along the runway adding to the uncertainty using normal recording rate video.

Deciding if this take-off was a “Free-Take-off”, let alone a pre-jump, would also be highly uncertain using normal video recording picture capture rate or even if the recording was made at the 50 pictures per second rate. Hence other means of determining the take-off toe tip breaking off from ground contact relative to the instant of pole tip collision with the box rear wall is required.

Pre jump 23.jpg (79.01 KiB) Viewed 40972 times

Jump 1147 by PSJ without doubt is a pre – jump take-off as revealed in the force –time graph data shown above. The reaction forces from the planting box exerted on the vaulter plus pole system are similar to those reported for male vaulter Rens Blom the winner of the IAAF 2005 World Pole Vault Championship. The temporal characteristics are also quite similar in regard to the time to maximum pole bend. The actual time interval of this pre-jump (PSJ Jump 1147) is shown clearly in the enlarged portion of the force time graph below of the time from toe tip take-off to pole tip impact with the rear wall of the planting box.

pre-Jump 15.jpg (56.71 KiB) Viewed 40972 times